1. Field of the Invention
This invention relates to a connector mounted on an end of optical fiber for transmitting a high energy beam, such as the laser beam, used for industries such as welding and soldering and for medical treatment such as cutting out affected parts.
2. Description of the Prior Art
Generally, on the incident and outgoing ends of an optical fiber used for transmitting this kind of high energy laser beam are mounted connector plugs so that the plugs are adapted to connect with receptacles one of which is at the incident end and contains a lens attached to a laser system and the other of which is at the outgoing end and contains a lens opposite to the object to be processed.
Such a plug of the conventional connector for a high energy beam is constructed as described below. FIG. 1 is a sectional view exemplary of a plug at the incident end side of the conventional connector for the high energy beam and FIG. 2 is a front view exemplary of the plug when viewed on the line II--II in the direction of the arrow in FIG. 1. Reference numeral 1 designates a cord containing therein a single optical fiber 1a, 2 designates a plug, and 3 designates a receptacle containing therein a lens 3a.
The cord 1 is cut out at sheath 1b of polyvinylchloride (P.V.C.), a Kevlar (trade mark of Dupont) 1c, and a jacket 1d of nylon to expose the Kevlar 1c, jacket 1d and an optical fiber 1a in a desired length, so that a plug body 21 is sleeved across an axially intermediate portion of the bared optical fiber 1a and the root portion of the bared jacket 1d.
The plug body 21 is made from stainless steel, formed in a cylindrical shape, provided at the outer periphery of an axially intermediate portion with a flange 21a, sleeved across the bared optical fiber 1a and jacket 1d, and fixed concentrically and integrally to the optical fiber 1a and jacket 1d through epoxy resin 21b filled between the inner periphery of body 21 and the outer periphery of optical fiber 1a. The bared Kevlar 1c covers the outer periphery of the root portion of plug body 21, and a skirt member 22 of stainless steel is sleeved on the sheath 1b and the root portion of plug body 21 so that the Kevlar 1c is sandwiched between the skirt member 22 and the outer periphery of the plug body 21 and fixed integrally thereto through a binder. In addition, reference numeral 23 designates a cap nut, which is screwably tightened to the outer periphery of the receptacle 3 in condition of inserting therein the utmost end portion of plug body 21, thereby insertably holding the plug body 21 to the receptacle 3.
As shown in FIG. 2, such a conventional optical fiber connector exposes at the utmost end face of plug 2 the epoxy resin 21b which concentrically integrally fixes the optical fiber 1a and plug body 21. Hence, when in the laser system lens 3a and optical fiber 1a are insufficiently aligned, the laser beam shifts from the incident end face of the optical fiber 1a so as to be projected on the epoxy resin 21b, whereby the epoxy resin 21b may burn to cause an escape or damage of the plug.
As a countermeasure for the above, an optical connector for a high energy beam has already been disclosed in the Japanese Utility Model Application No. 59-20146 (1984) by the inventors of the present invention. The optical connector disclosed therein is constructed so that the plug body 21 is divided into a holder and a sleeve. Combustibles are thereby eliminated from the vicinity of the laser beam incident end face of the sleeve supporting the fore end of optical fiber, so that even when the incident laser beam shifts, damage to the plug can be prevented.
FIG. 3 is a partially cutaway side view of the connector disclosed in the above described application and FIG. 4 is a schematic front view of the connector when viewed on the line IV--IV in the direction of the arrow in FIG. 3, in which reference numeral 31 designates a skirt member, 32 designates a holder, 33 designates a sleeve, and 34 designates a cap nut.
The sleeve 33 is cylindrical, made from copper, has at an axially intermediate portion an optical fiber support portion 33a of an inner diameter about equal to a diameter of the optical fiber 1a, has both axial end portions having a somewhat larger inner diameter than the optical fiber support portion 33a, and screws at a screw thread 33b formed at the inner periphery of the root portion with an utmost end of the holder 32 so that the sleeve 33 is connected thereto. The optical fiber 1a is held by the skirt member 31, holder 32, and optical fiber support portion 33a at the intermediate portion of sleeve 33, and is level at the utmost end face with the front end face of sleeve 33. In this construction, an annular gap 33c having a desired axial length from the end of optical fiber 1a, is formed between the sleeve 33 and the optical fiber 1a. Accordingly, even when the laser beam is incident shifting from the end face of optical fiber 1a, since there are no combustibles around the optical fiber 1a, the inconvenience of burning the connector can be prevented.
However, the optical connector having the construction described above allows the laser beam shifting from the end face of optical fiber 1a to be incident through the aforesaid gap 33c on the outer periphery of optical fiber 1a or the inner periphery of the larger diameter portion at the fore end of sleeve 33. When the laser beam is incident on the outer periphery of optical fiber 1a, some fusion is created on same, but leads to less breakage. However, when the laser beam is incident on the inner periphery of sleeve 33, the copper material for the sleeve 33 is molten and scattered to strike the outer periphery of optical fiber 1a, thereby creating a problem in that the optical fiber 1a may be cracked on the outer periphery rendering it breakable.